Hi Todd,
Trust me, you are not alone in finding crazy things done to your car by previous owners/hackers!!
The back dash should not be carpeted. As well, original models did not have speakers in rear.
I've replaced mine twice, here's why....I purchased an aftermarket back dash/package tray. It was vinyl covering a cheap cardboard-like material. My rear window leaked and that was the end of that.
Now, I've gone little beyond the norm. First, I had a metal support structure fabricated to go behind the rear seat and also hold two under-mounted speakers. I then purchased a piece of polycarbonate that was rigid, but still flexible enough to get into the original placement, which has a curve/bend to it. Before installing the poly (which is very easily trimmed with a jig-saw) I marked where the speakers were underneath and drilled a good amount of hole to allow the sound to penetrate through. On top of the clear poly I then glued (you can use 3M adhesive or just tape on the underside after stretching) black speaker fabric over the entire surface. This gives the black look (I have black interior) I needed as well as allows the sound to further penetrate through. This set up also hides the speakers so it maintains the clean look an impression of not having rear speakers.
The cost of the poly is about $60-$70 for the size you need. Speaker fabric is only a few dollars a yard.
Hope this helps!
Kirk